Tracers or duplicators for machine tools



April 2, 1963 F. w. ARMYTAGE TRACERS OR DUPLICATORS FOR MACHINE TOOLS 2Sheets-Sheet 1 Filed Nov. 19, 1958 April 2, 1963 F. w. ARMYTAGE TRACERSOR DUPLICATORS FOR MACHINE TOOLS Filed Nov. 19, 1958 2 Sheets-Sheet 2United States Patent Ofltice Patented Apr. 2, 1953 TRACERS R DUPLHIATQRSFOR MAQHINE T9015 Frederick W. Armytage, Lynwood, Racca Green,

Knottingley, England Nov. 13', 1958, Ser. No. 775,016

Claims priority, application Great Britain Nov. 1%, 1 57 4 (Claims. (Cl.25ll-3) This invention relates to tracers or duplicators for use withmachine tools and of the kind in which the movement of the tracerbutton, foot or stylus which follows the template or pattern actuates ahydraulic tracer valve which controls the flow of pressure fluid to andfrom the ram cylinder to produce a corresponding relative movementbetween the milling or other tool and workpiece.

The object of the present invention is to provide an im provedconstruction of such tracers or duplicators with a view to givinggreater sensitivity, accuracy and stability and enabling the degree ofsensitivity to be varied.

In carrying out this invention the tracer valve used must be capable ofbeing actuated by very small movements from the tracer foot of the orderof one thousandth of an inch. Such a valve is described and claimed inthe specification of my British Patent No. 692,642 and is the kind oftracer valve which will hereinafter be referred to in thisspecification, although any other suitable valve capable of beingactuated by such small movements might be used.

According to the present invention the construction is such thatdeflection of the stylus rod can be converted into reduced axialmovements of a slide valve member or spool by means of connectingelements which include a rotary cam or eccentric device. The stylus rodand valve member have their longitudinal axes parallel to one anotherand preferably co-axial with one another, and a rocker arm adapted to berocked by movement of the stylus rod is adapted to produce angularmovement of the rotary cam or eccentric and thereby to transmit aproportional reduced axial movement to the valve member. The proportionbetween the movements of the stylus rod and the valve member can bevaried at will within limits by adjusting the angular setting of the camor eccentric. I

The use of the rotary cam or eccentric device has a damping effecttending to prevent transmission of vibra tion from the valve member backto the stylus.

The stylus rod and rocker arm are controlled and steadied by springaction.

Spring pressure is necessary to obviate turbulence and vibration of thespool and stylus and to eliminate what is known as changeover faults,but this spring pressure may be applied to the rocker arm in variousways.

It is preferred to arrange for a spring housed in the spool (similar tothat in my British Patent No, 692,642 but not bearing upon the spool) tobear on a pressure rod which is freely slidable through the spool andwhich bears with its lower end indirectly on the top of the stylus rodthrough the intermediary of the rocker arm.

'In order that the invention may be more clearly understood and readilycarried into effect the same will now be more fully described withreference to and by the aid of the accompanying drawings, wherein:

FIGURE 1 is a vertical section through one construction of the tracerhead having valve actuating mechanism according to this invention, theview being taken in the direction of the arrows on line II in FIGURE 2.

FIGURE 2 is a view in the direction of arrow A in FIGURE 1 with thelower part of the tracer removed below line XX.

FIGURE 3 is a View similar to FIGURE 1 but showing only the centralportion of the tracer head and with a slightly modified construction ofthe valve actuating mechanism.

FIGURE 4- is a view in the direction of arrow B in FIGURE 3 with thelower part of the tracer removed below the line Y-Y.

FIGURE 5 is a full elevational view of the rocker arm shown in FIGURE 1.

FIGURE 6 is a full plan view of an actuating arm shown in FIGURE 1.

Referring to the illustrated examples of construction in which thestylus rod and valve member are mutually co-axial, the top part 1 of thetracer head supports a slide valve whose spool Z and valve spindle 3 arearranged for axial movement only.

This valve, as already explained, is preferably of the kind describedand claimed in the specification of my British Patent No. 692,642 and isindicated merely schematically in the present drawings. The stylus rod 4has a part spherical portion d by which it is supported on a partspherical seating 6 in the base of the tracer head so as to be rotatablethrough 360. This seating 6 is formed in a plate 7 secured by a flangedsleeve 8 which is inserted in and secured to a barrel portion 9 at thebase of the tracer head, these parts being constructed and arrangedsubstantially as described and claimed in the specification of my saidPatent No. 692,642, and my British Patent No. 757,589.

Between these two parts of the tracer head a two-part housing it), 11 issecured, part it) having a spigot 10x by which it is screwed to the toppart 1 of the tracer head and part Ell being screwed to barrel 9 bymeans of a screw-threaded connector sleeve 12;. The two housing partsiii, 11 are clamped together by screwed studs (not shown) inserted instud holes 13.

A piston member 14 has a skirt 15 which is axially slidable in theconnector sleeve 12 and a hardened ball 16 is held between coned faces17, 18 formed respectively at the top of the skirt 15 and on the top ofthe stylus rod 4, the top of rod 4 and the ball 16 having room forslight lateral movement.

Within the housing ill, 11 the flat top of the piston member 14 and aconed cap 19 hold between them a hardened ball 20 and the cap 19 isclamped in the split end of a rocker arm 21 whose other forked end isclamped on an eccentric shaft 22, on which is also secured an eccentriccam 23, this shaft 22 being journalled in bearing housings 24 supportedby bearing blocks 25 in the housing part it). This cam has a neat fit ina fork 26 which has a stud 27 by which it is clamped in one split end ofan actuating arm 28 whose other split end is clamped upon the valvespindle 3, so that angular movement of the cam causes axialreciprocation of the valve spool 2.

The angular position of the cam on its shaft can be altered as desiredwithin limits, thus altering the ratio of movement between the rockerarm 21 and the actuating arm 28 and hence the proportion between themovements of the stylus rod and valve member, but the trans mittedmovement will always be on a reduced scale.

The modified construction of the valve actuating mechanism shown inFIGURES 3 and 4 only differs from that of FIGURES 1 and 2 in respect ofparts 19, 20, 21 and 23. Instead of these parts, the rocker arm 21 isreplaced by a screwthreaded pin 30 screwed into the cam 23 and locked bynut 31, the .pin having a part spherical end 32 which is acted upon bythe piston member 14 in a similar way to the cap 19 and ball 20previously described, this .pin thus acting as the rocker arm. The shapeof the pin end may vary provided it offers as little friction aspossible in transmitting the movement of the stylus to the cam.

To steady the movement of the stylus rod and rocker arm a compressionspring 29 (see FIGURE 1) housed in the valve spool 2 is held by anadjusting screw 29a in a cap 29b secured in the top part 1 of the tracerhead and bears on a pressure rod 290 which is freely slidable throughthe spool and which bears with its lower end upon the cap 19 (or the pinend 32 as the case may be). This gives great sensitivity of control overthe movement of the stylus rod and at the same time allows the spool tomove more freely as it is not acting against direct spring pressure.Also this arrangement enables the valve spool to move with a smooth andpositive action over the very small distance required to reverse the oilflow to the ram, and so makes for greater accuracy and less risk ofchangeover faults.

The spring control of the stylus might be achieved satisfactorily byother constructions, for example by inserting a spring in the base ofthe tracer head surrounding the upper part of the stylus rod so as tobear down on the latter.

Important advantages given by this invention are a more stable action ofthe valve member as it is locked in any position by the cam therebydamping out reverse transmission of vibration or unwanted movement fromthe valve to the stylus rod, and increased accuracy at the point ofchangeover when oil is diverted from one end of the hydraulic ram to theother. Other suitable forms of connection between the stylus rod and therocker arm may be used as, for example, those described in my saidprevious patent specification.

I claim:

1. A hydraulic tracer mechanism for a machine tool comprising thecombination of a tracer head housing having two bores formed therein, atracer controlled valve member, a valve spindle mounting said valvemember tor axial sliding movement in one of said bores, a stylus rodmounted for valve actuating movement in the other of said bores, arocker arm mounted in the 4 housing for rocking movement in response toactuation by said stylus rod, said stylus rod and vlave member havingtheir longitudinal axes mutually co-axial, a movement transmittingassembly including a rotatably mounted eccentric cam device operativelyconnected to said stylus rod through said rocker arm and a shoe whichembraces and is operable by said cam device and which is positivelyconnected to said valve member, said movement transmitting assemblybeing effective to damp vibrations from said valve member back to saidstylus and to transmit small positive movements from the stylus to saidvalve spindle with proportionally reduced axial movement.

2. The combination as claimed in claim 1 wherein said movementtransmitting assembly further includes a spring housed in said valvemember and a pressure rod, said spring bearing on said pressure rod,said pressure rod being freely slidable through said valve member andthe lower end of said pressure rod bearing upon the top of said stylusrod through said rocker arm.

3. The combination as claimed in claim 2 wherein said movementtransmitting assembly further includes at least one set of co-actingconical surfaces and curved surfaces through which the top of saidstylus rod engages said rocker arm.

4. The combination as claimed in claim 3 wherein said movementtransmitting assembly further includes an axially slidable piston havingone of said conical surfaces which is co-axial with said stylus rod andvalve member, said piston having a sleeve portion fitting loosely overthe top of said stylus rod, and one of said curved surfaces comprising aball positioned between said conical surface on said piston and the topof said stylus rod.

References Cited in the file of this patent UNITED STATES PATENTS

1. A HYDRAULIC TRACER MECHANISM FOR A MACHINE TOOL COMPRISING THECOMBINATION OF A TRACER HEAD HOUSING HAVING TWO BORES FORMED THEREIN, ATRACER CONTROLLED VALVE MEMBER, A VALVE SPINDLE MOUNTING SAID VALVEMEMBER FOR AXIAL SLIDING MOVEMENT IN ONE OF SAID BORES, A STYLUS RODMOUNTED FOR VALVE ACTUATING MOVEMENT IN THE OTHER OF SAID BORES, AROCKER ARM MOUNTED IN THE HOUSING FOR ROCKING MOVEMENT IN RESPONSE TOACTUATION BY SAID STYLUS ROD, SAID STYLUS ROD AND VALVE MEMBER HAVINGTHEIR LONGITUDINAL AXES MUTUALLY CO-AXIAL, A MOVEMENT TRANSMITTINGASSEMBLY INCLUDING A ROTATABLY MOUNTED ECCENTRIC CAM DEVICE OPERATIVELYCONNECTED TO SAID STYLUS ROD THROUGH SAID ROCKER ARM AND A SHOE WHICHEMBRACES AND IS OPERABLE BY SAID CAM DEVICE AND WHICH IS POSITIVELYCONNECTED TO SAID VALVE MEMBER, SAID MOVEMENT TRANSMITTING ASSEMBLYBEING EFFECTIVE TO DAMP VIBRATIONS FROM SAID VALVE MEMBER BACK TO SAIDSTYLUS AND TO TRANSMIT SMALL POSITIVE MOVEMENTS FROM THE STYLUS TO SAIDVALVE SPINDLE WITH PROPORTIONALLY REDUCED AXIAL MOVEMENT.